The long term goals of this project are to arrive at a better understanding of how the central nervous system works to organize and control the limb movements involving more than one joint. The problems that arise in he organization and control of such movements concern questions such as: how is a point in space mapped into a proper set of joint angles so that the limb moves accurately to a target, how are the many muscles required to produced a movement coordinated, and what kind of feedback is appropriate to control multi-joint limb movements? This proposal deals with each of these problems. Psychophysical studies are planned to identify how information on the location of a point in extra-personal space and the orientation of the arm is represented within the central nervous system. Other experiments deal with the question: what are the rules which determine the proper level of activation of different muscles given a desired amount of torque. Results of these experiments should provide a better understanding of how the CNS normally controls movements and provide the basis for a better assessment of movement disorders and for the rational design of prosthetic devices.